Flow characteristics of gas-liquid adiabatic and boiling annular two-phase flows

A comprehensive understanding of annular flow characteristics is needed to improve the transport efficiency of petroleum and natural gas pipelines, and the efficiency and safety of heat transfer equipment, such as condensers, evaporators, steam generators, and nuclear reactors. For the annular flow characteristics, liquid film characteristics and wave characteristics are of essential importance for heat and mass transfer in annular flows. This paper reviews previous studies on these parameters, including prediction models and correlations for liquid film characteristics and wave characteristics of annular flows. Then, the paper examines the predictive capability of the models and correlations using existing databases. The data comparison considers the following aspects: the channel geometry effect, pressure effect, and heating state. The channel geometry affects the velocity profile, average film thickness, wave height, base film thickness, and wave frequency, while it has little effect on wave velocity. The pressure effect on these parameters is evident as it changes the gas inertia. For wave velocity in boiling flows, the predictions of current adiabatic flow models do not agree well with the current database values indicating the importance of heating state.